Well, honey, there ain't no such thing as a three-letter word with an apostrophe. Apostrophes are used for contractions or possessives in words, but they don't just hang out in three-letter words for fun. So, you can keep searching, but you won't find any three-letter words strutting their stuff with an apostrophe.
A contraction is made of two words with an apostrophe. Note the apostrophe replaces a letter.
It's
An apostrophe is not a letter. It falls into the punctuation category.
An apostrophe.
In contraction of words, the apostrophe is always placed at the spot where the letter(s) has been removed. In this case, at the place of the second o. do not: don't
I've
A contraction is made of two words with an apostrophe. Note the apostrophe replaces a letter.
It's
It's and He's
'tis
ne'er
It's
Some five letter words with an apostrophe are aren't, that's, and wasn't.
I've is a three letter word. I'll is another three letter word.
An apostrophe is not a letter. It falls into the punctuation category.
An apostrophe.
It is not a word. It is two words: "it will". The "i" in "it" is not pronounced, and that is why there is an apostrophe there. You will quite frequently see the letter "t" with an apostrophe in front in Shakespeare, and it always means "it".